KR20180020278A - Flux amount - Google Patents

Abstract

Providing a flux liquid capable of improving the hydrophilicity and sustainability of a heat exchanger formed by brazing a tube and a fin by soldering and improving solderability. Is a flux liquid 101 used for manufacturing a heat exchanger by brazing a tube 3 made of aluminum and a fin 2 made of aluminum. The flux liquid 101 contains a fluoride-based flux, colloidal silica, and a dispersion medium. The mass ratio of colloidal silica to the fluoride-based flux is 1/200 to 1/15.

Description

Flux amount

The present invention relates to a flux liquid used for manufacturing a heat exchanger by brazing a tube made of aluminum and a fin made of aluminum.

Generally, the all-aluminum heat exchanger has an aluminum tube through which the refrigerant flows and an aluminum fin for exchanging heat between the outside air of the tube, and the tube and the pin are joined to each other. Since the heat exchange performance of the heat exchanger greatly affects the hydrophilicity of the fin, a pin having a hydrophilic coating film on its surface is frequently used. For example, brazing is used to bond the pin and the tube having such a hydrophilic coating film.

However, since a general resin or inorganic coating film is denatured or decomposed at the heating temperature during soldering, sufficient hydrophilic property can not be exhibited after soldering. Further, when soldering is carried out using flux, the presence of a coating film may inhibit the fluxing action, which may result in insufficient solder jointing. Therefore, when a heat exchanger is manufactured by soldering, as shown in, for example, Patent Document 1, a coating film is formed after soldering. In this case, however, there is a problem in that a dedicated coating film forming equipment is required, which increases the manufacturing cost and makes it difficult to cope with the enlargement of the heat exchanger.

Thus, for the purpose of improving the hydrophilicity, for example, Patent Document 2 proposes a pin material having a coating film mainly composed of silicate as a fin material in which a coating film is pre-coated before soldering. Patent Document 3 proposes a method of manufacturing a heat exchanger using a fin previously provided with a coating film including a support such as xylene or a silicon-based binder such as silicone oil before soldering.

Patent literature

Patent Document 1: JP-A-2004-347314

Patent Document 2: JP-A-2013-137153

Patent Document 3: JP-A-2008-508103

However, even in the heat exchanger manufactured using the above-mentioned coating film or film-coated pre-coated fin, there is room for improvement in hydrophilicity after soldering using flux, and further improvement in initial hydrophilicity and persistence thereof is required. In addition, the presence of the precoated coating film or coating may lead to insufficient solder jointing of the fin and the tube using the flux.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a flux liquid which can improve the hydrophilicity and sustainability of a heat exchanger formed by brazing a tube and a fin and improve solderability.

One aspect of the present invention is a flux liquid used for manufacturing a heat exchanger by brazing a tube made of aluminum and a fin made of aluminum,

A fluoride-based flux, a colloidal silica, and a dispersion medium for dispersing the fluoride-based flux and the colloidal silica,

Wherein the mass ratio of the colloidal silica to the fluoride-based flux is in the range of 1/200 to 1/15.

The flux liquid contains a fluoride-based flux, colloidal silica, and a dispersion medium for dispersing the fluoride-based flux and the colloidal silica, and the content of the colloidal silica is adjusted to the above-mentioned predetermined range by mass ratio to the fluoride-based flux. Therefore, solderability in soldering can be improved and hydrophilicity can be imparted to the pin. That is, it has an effect of improving solderability and an effect of improving hydrophilicity. Therefore, the flux liquid is formed not only of a pre-coat type pin having a hydrophilic coating film on the surface of an aluminum fin (hereinafter referred to as "precoat fin" as appropriate) but also a bare type pin (Hereinafter referred to as " bear pin "). In either case, the effect of improving the hydrophilicity of the pin can be exhibited, together with the effect of improving the solderability. In addition, when the flux liquid is used for the bare pin, the solderability can be prevented from being impaired by the presence of the coating film. Further, since the hydrophilic property is imparted by the flux liquid, it is not necessary to form a coating film for imparting hydrophilicity to the film after soldering. Therefore, it is not necessary to provide a dedicated coating film forming equipment, and it is possible to prevent an increase in manufacturing cost, and also to cope with the enlargement of the heat exchanger. In addition, the effect of improving the hydrophilicity by the flux liquid includes not only the effect of improving the hydrophilicity at the initial stage of use but also the effect of continuing the initial hydrophilicity.

1 is a perspective view of a core portion (minicore) of a heat exchanger according to Embodiment 1. Fig.
Fig. 2 is a sectional view of a core portion (minicore) of the heat exchanger according to Embodiment 1. Fig.
3 is an enlarged cross-sectional view of the fin of the heat exchanger in the first embodiment.
FIG. 4 is an explanatory view (a) illustrating a cross-sectional structure of a fin and a tube before soldering and a cross-sectional structure of a pin and a tube after soldering; FIG.
5 is a front view of the heat exchanger in Embodiment 2. Fig.
6 is a perspective view of a core portion (minicore) of a heat exchanger in Modification 1. Fig.
7 is a sectional view of a core portion (minicore) of the heat exchanger in Modification 1. Fig.
8 is an enlarged cross-sectional view of a fin of a heat exchanger in Modification 1;
FIG. 9 is an explanatory view (a) showing a cross-sectional structure of a fin and a tube before soldering and a cross-sectional structure of a pin and a tube after soldering; FIG.

In this specification, " aluminum " is a concept including pure aluminum as well as aluminum alloy. That is, the material of the tube includes pure aluminum as well as aluminum alloy, and the material of the fin includes not only pure aluminum but also aluminum alloy. Specifically, pure aluminum of A1000 series, aluminum alloy of A3000 series, and the like can be used.

As the tube, a shape such as a round tube or a flat tube can be adopted. The inner tube may be formed in the tube to partition the inside into a plurality of passages. More specifically, for example, a flat pillar can be employed as the tube.

As the tube, for example, a tube formed by processing a brazing sheet into an annular tube shape or a flat tube shape can be used. The brazing sheet is made by cladding a brazing material to a core made of aluminum, and may be a one-side clad or a two-side clad. When a tube made by processing such a brazing sheet is used, it is not necessary to use a separate brazing material at the time of bonding. Therefore, it is preferable that the tube is a clad tube in which a brazing material is clad on the surface. As the brazing material to be clad in the core material, for example, Al-Si based alloy powder, Si powder, Al-Si-Zn based alloy powder and the like are used. Further, in the powder of the brazing material, the Si powder can exhibit its function as a brazing material by forming an Al-Si-based alloy contained in the tube and / or the fin when heating the brazing material. In addition, flux or a binder resin may be mixed with the above-mentioned brazing material. As the flux, for example, a fluoride-based flux powder such as potassium fluoroaluminate or potassium fluoroacetate is used. As the binder resin, for example, acrylic resin or the like is used. As the tube, a bear tube without cladding may be used.

As the pin, a shape such as a corrugate pin, a plate pin, a pin pin, or the like can be adopted. In order to improve the heat exchange performance, the fin may have a slit. As the fins, a clad pin having a cladding of a brazing material on the surface thereof, a precoat pin having a hydrophilic coating film formed on its surface, or a bare pin having no brazing material or a coating film may be used. When a clad pin is used, the same material as the above powder can be used as the brazing material, and the above-mentioned flux and binder resin may be mixed with the brazing material. The clad pin may be a one-side clad or a two-side clad. In the case of using a precoat fin, the hydrophilic coating film can be formed by applying a paint containing colloidal silica and drying it. The coating material for forming a hydrophilic coating film may also contain water glass and / or an organic resin. The hydrophilic coating film on the precoat fin may be formed on one side or on both sides.

Preferably, the pin is a clad pin or a bare pin. In this case, the effect of imparting the hydrophilic property of the flux liquid can be fully utilized, so that the hydrophilic property can be imparted even to the pin having no hydrophilic coating film. Further, in the case of the clad pin, it is not necessary to use a separate brazing material at the time of bonding.

A heat exchanger can be obtained by solder joining the tube and the fin. The soldering can be performed by supplying a brazing material to the joining portion of the tube and the fin and supplying the flux liquid to the joining portion or the fins and heating the joining portion. When a tube or a pin in which a brazing material is clad is used, since the brazing material is already supplied to the joint, it is not necessary to use a separate brazing material.

The flux liquid contains a fluoride-based flux, colloidal silica, and a dispersion medium for dispersing them. As the dispersion medium, for example, water can be used. As the fluoride-based flux, for example, potassium fluoroaluminate such as KAlF ₄ , K ₂ AlF ₅ , and K ₃ AlF ₆ can be used. As the fluoride-based flux, potassium fluoroacetate such as KZnF ₃ may also be used. As the fluoride-based flux, the above-mentioned compounds may be used singly or in combination. As the fluoride-based flux, for example, those having an average primary particle diameter of 1 to 50 nm can be used. The average primary particle diameter of the fluoride-based flux means the particle diameter at a volume integration value of 50% in the particle size distribution obtained by the laser diffraction / scattering method.

In the flux liquid, it is preferable that the mass ratio of the colloidal silica to the fluoride-based flux is 1/200 to 1/15. That is, it is preferable that the content C _F (mass part) of the fluoride-based flux and the content C _S (mass part) of the colloidal silica satisfy 1/200? C _S / C _F ? In the case of C _S / C _F <1/200, since the content of the colloidal silica is too small, there is a possibility that the hydrophilic persistence of the heat exchanger produced using the flux liquid becomes insufficient. It is more preferable that C _S / C _F ≥1 / 150 and C _S / C _F ≥ 1/100 from the viewpoint of further improving hydrophilicity sustainability. On the other hand, in the case of C _S / C _F > 1/15, the amount of the fluoride-based flux relative to the colloidal silica is too small and the solderability may become insufficient. And more preferably C _S / C _{F &lt;} / 20 from the viewpoint of further improving the solderability. Further, the preferred numerical ranges in this specification can be determined from all combinations of the upper limit and the lower limit.

The average particle diameter (that is, the average primary particle diameter) of the primary particles of the colloidal silica is preferably 1 to 800 nm. In this case, solderability and hydrophilicity can be improved to a higher level. The average primary particle diameter of the colloidal silica is more preferably 1 to 500 nm from the viewpoint of improving solderability and hydrophilicity to a more reliable and higher level. The average primary particle diameter of the colloidal silica is determined by drying the colloidal silica, determining its specific surface area using the BET method, and inversely calculating the weight and density from the specific surface area. The colloidal silica is dispersed in the flux liquid, for example, as a single particle or as an aggregate of particles.

Heating at the time of soldering is performed, for example, at an ultimate temperature of 570 캜 to 610 캜 in an inert gas atmosphere. By this heating, the brazing material is melted at the contact portion between the fin and the tube, and the melted brazing material is hardened by the subsequent cooling. This enables solder jointing of the pin and the tube.

The heat exchanger has a core portion made up of a fin and a tube brazed to the fin. A specific example of the heat exchanger will be described with reference to the drawings in the following embodiments, but the heat exchanger is manufactured by assembling a header, a side support, an inlet / outlet tube, etc. to the core portion.

The heat exchanger can be used, for example, in an air conditioner or a refrigerator. Also, it can be used for a capacitor, an evaporator, a radiator, a heater, an intercooler, an oil cooler, and the like of an automobile. It may also be used as a cooling device for cooling a heating element such as an IGBT (Insulated Gate Bipolar Transistor) provided in an inverter unit for controlling a driving motor for a hybrid vehicle or an electric vehicle.

Example

(Example 1)

This example is an example in which a plurality of flux solutions according to the examples and the comparative examples are manufactured and the performance thereof is compared and evaluated. Concretely, the core portions for a heat exchanger are manufactured by using these flux solutions, respectively, and solderability and hydrophilicity (that is, initial hydrophilicity and hydrophilicity persistence) are evaluated. In this example, a test mini core is manufactured as a core part.

As shown in Figs. 1 and 2, the minicore 1 has a fin 2 and a tube 3, and a pin 2 in the form of a corrugate is fitted in the tube 3. 1, one of the two tubes 3 that sandwich the fin 2 is indicated by a dashed line in order to specify the corrugated shape of the fin 2. As shown in Fig. 1 to 3, the fin 2 has a fin material 21 made of an aluminum plate molded in a corrugated shape and a brazing filler metal layer 22 clad on both sides of the fin material 21.

As shown in Figs. 1 and 2, the tube 3 is made of a flat pore tube made of an aluminum alloy. The tube (3) has a plurality of refrigerant flow paths (311) for circulating the refrigerant. In the mini core 1, as shown in Fig. 4 (b), the fins 2 and the tube 3 are solder jointed, and a joint portion 100 is formed between them.

Hereinafter, a manufacturing method of the mini-core 1 of the present embodiment will be described. Concretely, a brazing sheet in which a brazing material made of an Al-Si alloy is clad on both surfaces of a plate-like core material made of an aluminum alloy as a fin material is first prepared, and then the brazing sheet is processed into a corrugated shape. Thus, the fin 2 clad on both sides of the fin material 21 made of the aluminum plate was obtained as the brazing filler metal layer 22 (see Figs. 1 to 3). Subsequently, a tube 3 made of a flat multi-hole tube made of a 3000-series aluminum alloy was produced by extrusion processing (see Figs. 1 and 2).

Next, a pin 2 of a corrugated shape was inserted between the two tubes 3 to manufacture an assembly (see Figs. 1 and 2). As a result, the brazing material layer 22 at each apex 20 of the corrugated fin 2 was brought into contact with the surface of the tube 3.

Next, each flux liquid having the composition shown in Table 1 described later was prepared, and the flux liquid 101 was applied to the assembly 2 composed of the fins 2 and the tubes 3, as shown in Fig. 4 (a) And sprayed all over. Thereafter, the assembly was held in an in-furnace at a temperature of 600 DEG C in a nitrogen gas atmosphere for 3 minutes and then cooled to room temperature (25 DEG C). At the time of heating in this furnace, the filler metal layer 22 of the fin 2 is at least partially melted and the melted filler metal layer 22 is hardened at the time of cooling. By fusion and curing of the filler layer 22, the fins 2 and the tube 3 are joined at the contact portion to form the joint portion 100 (see Fig. 4 (b)). Thus, mini core 1 was obtained as shown in Figs. 1 and 2. In this example, as shown in Table 1, a plurality of mini-cores 1 were manufactured by using a plurality of fluxes having different compositions. NOCOLOK used as a fluoride-based flux in Table 1 to be described later is a product manufactured by SOLVAY, and FL7 is a product manufactured by Morita Kakuko Kogyo Co., Ltd. As the colloidal silica, Cataloid SI-550 which is amorphous colloidal silica manufactured by Nikkiso Co., Ltd. was used. The flux liquid was prepared by dispersing colloidal silica and a fluoride-based flux in water as a dispersion medium in the blend shown in Table 1. The amount of the dispersion medium may be suitably adjusted so as to be a viscosity suitable for application.

Next, each of the mini-cores obtained as described above was evaluated for solderability, initial hydrophilicity and hydrophilicity sustainability. The results are shown in Table 1.

<Solderability>

(L ₁ / L ₂ × 100), which is expressed by a percentage of 100, is obtained by cutting the soldered joint portion in each of the minicores by a cutter knife and dividing the joint length (L ₁ ) of the pin by the sum of the peak length (L ₂ ) (%). &Lt; tb &gt;&lt; TABLE &gt; The case where the bonding ratio was 90% or more was evaluated as "A +", the case where the bonding ratio was 70% or more and less than 90% was evaluated as "A", and the case where the bonding ratio was less than 70% was evaluated as "B".

<Initial hydrophilicity>

The evaluation of the initial hydrophilicity was carried out using a plate test plate having the same structure as the pin. That is, the flux of each sample was sprayed on the test plate, and heating was performed on the assumption of soldering. Specifically, the test plate on which the flux liquid was sprayed was heated in a furnace at a temperature of 600 占 폚 for 3 minutes in a nitrogen gas atmosphere. Then, the hydrophilicity was evaluated by measuring the contact angle of water droplets on each test plate. The contact angle was measured using a FACE automatic contact angle meter "CA-Z" manufactured by Kyowa Hakko Kakuga Co., Ltd. Specifically, water droplets were dropped onto the test plate at room temperature, and the contact angle of water droplets after 30 seconds was measured. A case where the contact angle is 20 DEG or less is evaluated as &quot; A &quot;, a case where the contact angle is more than 20 DEG and 30 DEG or less is evaluated as &quot; B &

<Continuity of hydrophilicity>

The above-mentioned test plate was immersed in pure water for 2 minutes and then air-dried for 6 minutes. This immersion in pure water and the wind drying cycle were repeated 300 times. Thereafter, the contact angle with the water droplet was measured in the same manner as the evaluation of the above-mentioned hydrophilicity. A case where the contact angle after 300 cycles was 25 DEG or less was evaluated as &quot; A &quot;, a case where the contact angle was more than 25 DEG and less than 40 DEG was evaluated as &quot; B &

As can be seen from Table 1, when the flux solutions of Samples 1 to 16 were used, both solderability, initial hydrophilicity and hydrophilicity persistence were excellent. On the other hand, Samples 17 to 19, which did not contain colloidal silica, showed poor hydrophilic persistence. Samples 20 to 27 having a small amount of colloidal silica relative to the amount of fluoride-based flux were improved in hydrophilicity persistence as compared with Samples 17 to 19, but persistence was still insufficient. In addition, the samples 28 to 35, which had a large amount of colloidal silica relative to the fluoride-based flux amount, were poor in solderability.

Therefore, it is preferable to use a flux solution containing a fluoride-based flux, colloidal silica, and a dispersion medium and having a mass ratio of colloidal silica to fluoride-based flux of 1/200 to 1/15 as in Samples 1 to 16 Which is preferable. When such a flux liquid is used to manufacture a heat exchanger by brazing a tube made of aluminum and a fin made of aluminum, it becomes possible to manufacture a heat exchanger excellent in solderability, initial hydrophilicity and hydrophilicity sustainability. In this example, the pin 2 has the filler layer 22, and the pin 2 is a clad pin. Therefore, it is possible to solder joint without separately supplying a brazing material.

(Example 2)

Next, an example of the heat exchanger will be described. As shown in Fig. 5, the heat exchanger 4 has a core portion 10 having many of the same structures as the minicoler described in the first embodiment. Specifically, the core portion 10 is formed by laminating a plurality of corrugated fin 2 and a tube 3 alternately, and the fin 2 and the tube 3 are stacked on the mini core of Example 1 And is also soldered.

A header 5 is assembled at both ends of the tube 3 and a side plate 6 is assembled at both ends (outermost side) in the stacking direction of the core portion 10. [ In addition, a tank 7 is assembled to the header 5. The header 5, the side plate 6 and the tank 7 can be joined by, for example, soldering, in the same manner as the above-described bonding of the fin 2 and the tube 3.

In the heat exchanger 4, solder bonding can be performed using the same flux liquid as that of the samples 1 to 16 in the first embodiment. As a result, the heat exchanger (4) obtained after soldering has excellent solderability between the fin (2) and the tube (3), and is excellent in initial hydrophilicity and hydrophilicity sustainability.

(Modified Example 1)

In the first embodiment, the mini-core in which the bare tube and the clad pin are joined has been described. In this example, however, the minicore in which the clad tube and the bare pin are joined is described. 6 and 7, the mini-core 1 has a pin 2 and a tube 3 in the same manner as in the first embodiment, and a pin 2 of a corrugated shape is fitted in the tube 3 . As shown in Figs. 6 to 8, a brazing material layer or the like is not formed on the surface of the fin 2, and the fin 2 is a bare pin.

As shown in Figs. 6 and 7, the tube 3 has a core 31 made of a flat porous tube made of an aluminum alloy, and a brazing material layer 32 formed on the surface of the core 31. Fig. The core member (31) has a plurality of refrigerant flow paths (311) for circulating the refrigerant. As shown in Fig. 9 (b), the fins 2 and the tube 3 are solder jointed, and a joint portion 100 is formed between them.

Hereinafter, a manufacturing method of the mini-core 1 of the present embodiment will be described. Specifically, first, a plate-like aluminum plate of A1050 composition according to JIS standard was processed into a corrugated shape. Thus, a pin 2 having a corrugated shape was obtained (see Figs. 6 to 8).

Subsequently, a core member 31 made of a flat multi-hole tube made of a 3000-series aluminum alloy was produced by extrusion processing (see Figs. 6 and 7). Then, the brazing material layer 32 was formed by applying a brazing material composed of Si powder to the surface of the core material 31. [ Thus, a tube 3 was obtained.

Next, a pin 2 of a corrugated shape was inserted between the two tubes 3 to manufacture an assembly (see Figs. 1 and 2). At this time, the pin 2 is sandwiched between the two of the tubes 3 of the tubes 3 so as to face each other, Lt; / RTI &gt; Then, as shown in Fig. 9 (a), the flux liquid 101 was sprayed onto the entire assembly consisting of the tube 3 and the fins 2. Then, Thereafter, the assembly was held in a furnace at a temperature of 600 ° C in a nitrogen gas atmosphere for 3 minutes, and then cooled to room temperature (25 ° C). During the heating in the furnace, the filler layer 32 is melted, and the melted filler layer 32 is cured at the time of cooling. By fusion and curing of the filler layer 32, the fins 2 and the tube 3 are joined together to form the joint portion 100 (see Fig. 9 (b)). In this way, mini core 1 was obtained as shown in Figs. 6 and 7. Fig. Also in this example, the same results as in Example 1 were obtained when the solder joint was performed using the same flux liquid as in Example 1. [ That is, by using the flux solutions of Samples 1 to 16, solderability, initial hydrophilicity, and hydrophilicity persistence were improved as compared with the case of using Samples 17 to 35.

As described above, the embodiments and modifications of the present invention have been described in detail. However, the present invention is not limited to these examples, and various modifications can be made without departing from the spirit of the present invention.

Claims (4)

As a flux liquid used for manufacturing a heat exchanger by brazing a tube made of aluminum and a pin made of aluminum,
A fluoride-based flux, a colloidal silica, and a dispersion medium for dispersing the fluoride-based flux and the colloidal silica,
Wherein the mass ratio of the colloidal silica to the fluoride-based flux is 1/200 to 1/15. The flux liquid according to claim 1, wherein the primary particles of the colloidal silica have an average particle diameter of 1 to 500 nm. The flux liquid according to claim 1 or 2, wherein the fin is a clad pin whose surface is clad on the surface. The flux liquid according to any one of claims 1 to 3, wherein the tube is a clad tube in which a brazing material is clad on the surface.

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